Because later the writers still had to slowly and painfuly defile Cordelia's character....🙁
[MENTION=7336]ILLYRIAN[/MENTION]
I have not medical knowledge at all, but I think that if she survived then no organ were damaged. And if I remember right this is what Buffy and Willow say right after that scene, they comment on Cordy being at hospital but no organs were hit..dunno if I remember right though.